The department is prohibiting both men from driving commercial vehicles in the United States, alleging that speeding played a part in the crash that killed nine and injured dozens more on Interstate-84 near Pendleton, Ore., on Dec. 30.
The U.S. regulator body says Mi Joo Tour and Travel's driver Haeng Kyu (James) Hwang was driving too fast for the icy road conditions when he lost control and his bus plunged down an embankment.
A second driver, Choong Yurl Choi, who was in a separate bus and working on the same trip for the Coquitlam, B.C., company, is also accused of driving too fast for the conditions.
On Jan. 8, the tour company was ordered to stop operating in the United States.
"We will not tolerate illegal and unsafe behaviour by bus and truck drivers," said U.S. Department of Transport secretary Ray LaHood in a news release.
"Safety for every traveller on our highways and roads is our highest priority."
In its continuing investigation, the department said both drivers were found to have been driving well beyond the 70-miles-an-hour limit.
Anne Ferro, the administrator for the U.S. Federal Motor Carrier Safety Administration, said interstate bus and truck companies and their drivers should have no doubt that her department will vigorously enforce safety regulations.
"Carriers and drivers who flout the safety rules put the public at risk and will be shut down."
Police have not yet said what caused the crash, so the federal department's assessment of excessive speed is the first suggestion of what may have contributed to the tragedy.
Eight survivors have now joined an American lawsuit alleging Mi Joo Tours and its drivers committed "wilful and wanton misconduct," while a couple from Burnaby have filed a separate suit in a B.C. court.
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